Hologram Technique After Photographic method...!!!

2. INTRODUCTION
In this method a lens focuses the
light reflected from a three-
Images of objects are generally dimensional object onto a
obtained using photographic method. photographic film where a two-
dimensional image of the object is
formed.

3. A –ve is first obtained by
developing the film and then a
+ve is obtained through printing.
It contains information about the
square of the amplitude of the The +ve print is a two-
light wave that produced the dimensional record of light
image but information about the intensity received from the
phase of the wave is not object.
recorded & lost.

4. It is radically a new
In 1948 Dennis Gabor technique of
outlined a two-step photographing the The technique is also
lenseless imaging objects & is known as called holography.
process. wave front
reconstruction.

5. The word holography is
formed by combining
parts of two Greek
words: „holos‟, meaning
“whole”, & „graphen‟
meaning “to write”.
Thus holography means
writing the complete
image.

6. HOLOGRAPHY MEANS:
In this process both
It is a recording of
the amplitude &
interference pattern
phase components
formed between The recording is
of light wave are
two beams of known as a
recorded on a light
coherent light hologram.
sensitive medium
coming from the
such as a
same source.
photographic plate.

7. PRINCIPLE
Holography is a
two-step
process.
The second step First step is the
is the recording of
reconstruction in hologram where
which the the object is
hologram is transformed into
transformed into a photographic
the image. record.

8. A Hologram is the result of
interference occurring between two
waves,
an object beam which is the light
scattered off the object & a coherent
background,
the reference beam, which is the light
scattered off the object & a coherent
background, the reference beam ,
which is the light reaching the
photographic plate directly.

9. Making a Hologram

10. Beam splitter
mirror
mirror
Beam spreader

11. PROPERTIES
Photography, is an ordinary
photograph each region
contains separate & individual
part of the original object.
Therefore, destruction of a
portion of a photographic image
leads to an irreparable loss of
information corresponding to
the destroyed part.
On the other hand, in a
hologram each part contains
information about the entire
object

12. Conventional photography vs. Holography
Conventional photography
2-d dimension Film sensitive
of a 3-d scene only to intensity
(object). distribution.
Photograph
lacks depth
perception.

13. Conventional photography vs. Holography
Hologram:
 3-d dimension of a 3-d scene.
 Not only the intensity distribution of reflected light is
recorded but also the phase distribution.
 To view a hologram, the wavefront is reconstructed.
Viewed from different angles, the object is
also seen from different angles.

14. Conventional photography vs. Holography
Hologram:
 Converts phase information into
amplitude information (in-phase -
maximum amplitude, out-of-phase
– minimum amplitude).
 Interfere wavefront of light from
object beam with a reference
wave.
 The hologram is a complex
interference pattern . It‟s a kind of
diffraction grating.
If you tear a hologram in half, you can still see the whole image in each piece.The
same is true with smaller and smaller pieces.

15. APPLICATIONS
Holography is widely used in non-
destructive testing to study
distortions resulting from
stresses, strains, heat & vibrations
Holographic Interferometer
etc. In the double exposure
technique two exposures are made
of the object, one before processing
& the other after.

16. Supermarket and
The use of holograms Medical doctors can
department store
on credit cards and use three-dimensional
scanners use a
debit cards provide holographic CAT scans
holographic lens
added security to to make
system that directs
minimize measurements without
laser light onto the bar
counterfeiting. invasive surgery.
codes of the product.

17. ACOUSTIC HOLOGRAPHY
It is easy to produce coherent
sound waves. Sound waves
readily propagate in solids.
Therefore, a three
dimensional acoustical
hologram of an opaque object
can be made.
By viewing such hologram in
visible light the internal
structure of the object can be
observed.

18. HOLOGRAPHIC OPTICAL ELEMENTS
Holographic optical
elements (HOE) are HOEs perform
diffractive devices precisely the same
which are holograms type of operation as
of typical optical the lenses or
components such as mirrors,
lenses or mirrors.
They are used in
but they do it by
barcode scanners,
diffraction and not by
office copy
refraction or
machines, solar
reflection.
concentrators, e.t.c.